Just about all of the theories of education start from the premise that the lessons, textbooks, and tests are 100 percent valid in teaching and evaluating students in an educational environment.
Having studied many diverse subjects in classes and in independent study, I can report that many textbooks, as well as classroom environments, are mediocre at best.
When I studied a subject, my intention was to learn enough about it to be satisfied with my efforts. I evaluated my learning efforts myself because I was motivated to learn.
The only valid way to evaluate whether someone has learned something is to see if they can DO something useful with the knowledge that they have supposedly gained.
Can the student write a coherent essay, give an understandable lecture, write a valid computer program, play a musical instrument, perform a dance, act in a play, repair a car?
Just reading a textbook, doing lessons, and passing a multiple choice test doesn't imply any useful learning took place.
The most important factor in learning (and the most neglected) is the motivation of the student to learn.